Method of rolling sheet metal packs



March 19, 1935. A. PATERSON METHOD OF ROLLING SHEET METAL PACKS Filed June 1, 1934 rm, Stand NUMBER OF PASSES Secuncb y W4 INVENTOR dfe ravzclerfifevson BY M JX/ .y l ATTORNEY Patented Mar. 19, 1935 UNITED-mares AlENT OFFICE Alexander Paterson, Buffalo, N. Y.

Application June 1, 1934, Serial No. 728,545

l Claims.

various factors, which determine the shape of the pack and the individual sheets thereof, are involved. These factors include the initial shape and temperature of the pack, the permissible distortion or change in the cross-section or shape of the individual sheets in the pack during the rolling operations, the contour of the rolls and of the working pass provided thereby and the resiliency of the rolls or their resistance to deflection. In order to counteract roll deflection, which is caused by the bending stresses set up during the rolling operations and which is greats est at the central zones of the working rolls, it is the practice to increase the diameter of the rolls at their central zones. Preferably the increase in the diameter of the central zones of the rolls is limited so'that during the initial heavy reductions the rolls provide a working pass of convex cross-section while duringthe succeeding lighter reductions the working pass approaches a cross-section which is substantially fiat or rectangular. In other words, the cross-section of the working pass is dependent upon the magnitude of the reduction. Hreretofore, owing to the diificulty encountered in fitting a pack to the various sets of the rolls of a tandem pr continuous mill with such accuracy as to insure maintenance of the distortion of the individual sheets within the permissible zone of tolerance, it has been the practice to effect the successive reductions by passing and repassing the pack through the rolls of a single stand mill. TIhis mode of procedure is preferable in the case of pack rolling as it eliminates the difiiculties attendant upon the accurate fitting of the pack to various sets of working rolls, it being understood in this connection that unless the pack fits the pass provided by the working rolls within a narrow range of tolerance the various sheets of the pack wil be distorted and cannot be separated Without injury. In the ordinary mill the pack, after being heated, is given four or five passes between the rolls of the stand, the screws being set between passes to regulate or control the magnitude of the reductions. The greatest reduction is obtained in the first pass, the screws being adjusted for this pass so that thereduction obtained corresponds to the maximum permissible deflection of the rolls. In the succeeding passes the screws of the 'standare adjusted so that the magnitude of the deflection of therolls is progressively decreased to decrease the convexity of the. pack correspondingly and cause it to approach a flat or rectangular cross-section, It will be apparent, therefore, that after the first pass the magnitude of the screw adjustment is determined to a large degree by the resiliency of the rolls. Thus substantially the entire capacity of the stand for each series of reductions is utilized in the first pass whereas in the succeeding passes only a fraction of the capacity of the stand is availed of owing to the fact that the roll factors, which are predetermined to eiiect the greatest reduction in the first-pass, remain substantially constant. The magnitude of the reductions, therefore, progressively decreases. Any attempt to eiiect reductions in the succeeding passes equal in magnitude to those in the first pass would, therefore, result in distortion of the individual sheets beyond the permissible zone of tolerance. Owing to the rapidity at which the pack cools the decrease in the magnitude of the reductions cannot be compensated by increasing the number of passes as after four or five passes the amount of reduction obtained in a single stand of rolls without reheating is practically. negligible. V

The principal object of the present invention is to overcome the' above objections, this object contemplating a novel method of rolling whereby, with respect to a single heating, a maximum reduction of the pack is obtained without injury to the individual sheets thereof.

A further object is a process which can be carried out by existing equipment.

The invention is illustrated in ing drawing in which: v

Figure 1 is a view partially in elevation and partially in section of a mill for' carrying out my process.

Figure 2 is an exaggerated diagrammatic view illustrating the shape of the pack and the working rolls during the first pass.

Figure 3 is a similar view illustrating the shape of the pack and the working rolls during the third pass. i

Figure 4 is a graphic illustration of the magnitude of the reductions obtained inthe stands of the mill shown in Fig. 1.

the accompany- Figure 5 is a view inelevationoi a three-stand the kind covered by my Patent No. 1,953,190 issued April 3, 1934, and as illustrated, are iormed or provided with end collars 12 and intermediate collars 13, the latter'preferably being of a suitworking rolls may be regulated to form a'pack with a predetermined cross-sectional convexity by varying the relative diameters of the said collars. For example,- by increasing the diameter of an intermediatecollar- 13 of a backing roll or by decreasing the diameters of the end collars 12 or by effecting both of these variations simultaneously, the degree of deflection of the central zoneof the associated working roll will be reduced with a corresponding reduction in the cross-sectional convexity of the pack. As noted'inmy said Patent No. 1,953,190 the variations necessary in the diameters of the collars to obtain the necessary amount of control will for most purposes be ofthe order of a few thousandths of an inch and such variations can, therefore, be readily obtained by the use of suitable heating and cooling devices. g

The primary-stand of rolls 5 is preferably a hot mill and is designed with reference tothe initial shape of the pack which. is to be reduced, that is to say the factors which determine the magnitude ofthe reductions and the cross-sectional contour of the pack are predetermined to effect, in the first pass, the maximum permissibledeflection of the working rolls (see Figure 2), and hence the maximumpermissible reduction of the pack. Assuming, for example, that the factors involved are predetermined'with respect to a four-sheet pack having an initial thickness of .250" and that thesaid pack is to be reduced to a thickness. of .084", then in the first pass between'the working rolls of the stand 5, approximately 42% of the total amount of reduction will be effected (see curve 14 of Figure 4). Approximately 21% of the total reduction will be effected in the second pass while approximately 10.8% and 5.4% would be effected in the third and fourth passes, respectively, in the said stand. It will be apparent that while in the first pass the maximum capacity of thestand is utilized, this cannot be done in the succeeding passes as the deflection of the working rolls must be progressively decreased in order to prevent distortion of the individual sheets of the pack. -'In thefourth pass the thickness of the pack would be reduced to approximately ;.117" and the pack would be formed with a cross-section which is substantially fiat or rectangular. Hence regardless of the number of additional passes further reductions could not be obtained without reheating and rerolling the pack. In progressively decreasing the degree of deflection of the working rolls as de scribed, the magnitude of the reductions are correspondingly reduced. Thus, whereas in the first two passes of the total required reduction is obtained only 16.2% of the total reduction could be obtained in the final two passes in the same stand. In ordentherefore, to reduce the pack to the desired thickness, i. e., .084, it would be necessary to first reheat it and then further roll'it.

In carrying out my process a pack 15 of the dimensions above noted after being heated in any suitable manner is passed twice between the working rolls of the stand 5, thereby effecting two major reductions or approximately 70% of the required reduction, the diameters of the collars 12 and-13 of the backing-ro1l 9-being"regulated or controlledso that the said pack is formed with a predetermined cross-sectional convexity in its second pass between the working rolls. Immediately thereafter, and without reheating, the

pack is passed and repassed between the working rolls of the. adjacent secondary stand 6, the num ber of such passes being determined by the amount of reduction to be effected in this stand and in the example given being four. The secondary stand may be either a hot mill or cold mill such as, for example, awatermill, and the rollsthereof are adapted to provide a series ,of

reducing passes which areflattengthatis to say less convex, than the corresponding passes of the series provided by the working rolls of thestand 5. The secondary stand of rolls 6 is designed with reference to the shape ofthe pack; 15 as modified by the rolls of the stand5=in order that two major reductions will be obtained in the first two passes, the collars 12 and 13 of the'backing roll 9 providing means for regulating or controlling the cross-sectional contour of theworking pass so that'it may be made to conform tothe changed shape of the pack.: In this connection it is understood, of course, that'the degree of deflection of the working rolls is small and that the deflection shown in Figures2 and3 is greatly exaggerated in order to render-the illustrations more clear. The roll factors of the secondary stand being. predetermined with respect. to the shape or cross-section of the pack as modified by the rolls of the first stand, the. maximum permissible deflection of. the working rolls is obtained,

and hence the maximum permissible reduction f of ,the pack is effected in the first pass. In this pass approximately 20% of the total reduction is effected (see curve 16 of Figure 4) j Inthe second pass approximately 14% of the total reduction is effected while in the third and fourth passes the pack is reduced approximately 10% and: 5%,

respectively, ofthe total amount required. In

the final pass the pack is reduced to the'requiredthickness, 1. e., .084", the total reduction being effected, therefore, in six passes and requiring only one heating of the pack. 7 1

It will be apparent upon comparing curves 14 and 16 that whereas approximately 17.3% of the total amount of reduction of the pack is obtained in the first pass in the secondarystand fionly approximately 10.8% could have been obtained as a third pass in the primary stand 5; that Whereas approximately 10% of the total reducf tion is obtained in the second pass in the second ary stand only approximately 5.4%, could have been; obtained as a fourth pass in the primary stand; and'that whereas approximately 9% of the total reduction is obtained in the final two passes in the secondary stand no equivalent reduction could beobtained in the primary stand without reheating the pack owing to the exhaustion of the resiliency of the working rolls. In other words, by following the; procedure described approximately 28.2% greater reduction is obtained; in the example given, than would'be obtained upon a single stand mill with a single heating of the pack. 7 y

In order to decrease the time between passes;

and thereby reduce heat loses by radiation the leading end of the pack may, as it emerges frombetween the working rolls of a stand, be guided back over the top roll thereof so that in the succeeding pass in the stand it becomes the trailing end of the pack. Any suitable apparatus may be employed for this purpose. For example, as the pack emerges from the rolls it may be directed by a guide over the top of the upper working roll, the leading end being engaged by a magnetic roller which returns the pack to a point from which it may be reintroduced between the rolls as described.

A modified form of mill for carrying out the process is shown in Figure 5. The mill, as illustrated in this embodiment, includes a primary stand 1'7 and secondary stands 18 and 19. Each of the said stands includes upper and lower working rolls 20 and 21, respectively, and backing rolls 22 which are associated with the lower working rolls. The backing rolls 22 are formed or provided with end collars 23 and intermediate collars 24, the said collars co-operating with the associated working rolls to regulate or control the degree of deflection of the latter as described in connection with the mill shown in Figure 1. The stand 17 is similar to the stand 5 of the mill shown in Figure 1 while the stands 18 and 19 are both similar to the stand 6 of the said mill.

In carrying out the process the first pack to be reduced is passed between the working rolls of the primary stand 17 to efiect two major reductions. Thereafter the said pack is immediately introduced between the working rolls of either of the adjacent secondary stands 18 and 19 while a second pack is introduced between the working rolls of the primary stand 1'7. Upon completion of the two major reductions of the second pack in the primary stand 1'? and while the first pack is receiving its third pass, or minor reduction, the said second pack is introduced immediately between the working rolls of the other of the secondary stands. The use of three stands in the manner described, therefore, has the advantage that the primary stand 17 may be worked continuously, which, of course, cannot be done where only two stands are employed as only two passes are made in the primary stand while in many cases four passes will be made in the secondary stand. When the packs are formed of two or three sheets, the individual sheets may, if desired, be first given a single pass through the rolls of the primary stand 5 and then piled and given one or two passes through the rolls of the said stand prior to the rolling of the packs in the secondary stand 6.

From the foregoing it will be apparent that the practice of the process enables a substantially greater reduction of a pack, with respect to a single heating, than can'be obtained by conventional rolling methods. Moreover, distortion or injury to the individual sheets of the pack is avoided owing to the predetermination of the roll factors and the accurate control of roll deflection by the collars of the backing rolls. The backing rolls of the mills shown in the two embodiments described may be substituted for the conventional backing rolls of standard mills. The process, therefore, has the further advantage that its practice may be carried out with existing mills, the latter being readily adaptable to the present method.

Having fully described my invention, I claim:

1. The method of rollinga sheet metal pack to reduce it to a predetermined thickness and crosssectional contour, which method consists in passing the pack at least twice through a stand of rolls having roll factors predetermined with respect to the initial shape or cross-section of the pack, whereby to effect two major reductions While forming the pack with a predetermined cross-sectional convexity and passing and repassing the pack through a second stand of rolls having roll factors predetermined with respect to the shape or cross-section of the pack as modified in the last pass through the rolls of the first stand, whereby to effect in the second stand two major reductions in the first two passes and such minor reductions in the succeeding passes as may be required to reduce the pack to the thickness and cross-sectional contour which has been predetermined. r v

2. The method of rolling a sheet, metal packto reduce it to a predetermined thickness and crosssectional contour, which method consists in heating the pack, passing it twice through a stand of rolls having roll factors predetermined with re spect to the initial shape or cross-section of the pack, whereby to effect two major reductions while forming the pack with a predetermined cross-sectional convexity and passing and re-- passing the pack without reheating through a second stand of rolls having roll factors predetermined with respect to the shape or crosssection of the packas modified in the second pass through the rolls of the first stand, whereby to eiiect in the second stand two major reductions in the first two passes and such minor reductions in the succeeding passes as may be required toreduce the pack to the thickness and cross-sectional contour which has been predetermined.

3. The method of rolling a sheet metal pack to reduce it to a predetermined thickness and cross-sectional contour, which method consists in heating the pack, passing it twice through a stand of rolls having roll factors predetermined with respect to the initial shape or cross-section of the pack, whereby to effect two major reductions while forming the pack with a predeter mined cross-sectional convexity and passing and repassing the pack, without reheating, at least three times through a second stand of rolls having roll factors predetermined with respect to the shape or cross-section of the pack as modified in the second pass through the rolls of the first stand, whereby to effect in the second stand two major reductions in the first two passes and one minor reduction in the succeeding pass and thereby reduce the pack to the thickness and cross-sectional contour which has been predetermined.

reduce it to a predetermined thickness and crosssectional contour, which method consists in heating the pack, passing it twice through a stand of rolls having roll factors predetermined with respect to the initial shape or cross-section of the pack, whereby to efiect at least 40% of the total amount of reduction required and at the same time forming the pack with a predetermined cross-sectional convexity and passing and repassing the pack, without reheating, through a second stand of rolls having roll factors predetermined with respect to the shape or cross-section of the pack as modified inthe second pass through the rolls of the first stand, whereby to effect in the second stand two major reductions in the first two passes and such minor reductions in the succeeding passes as may be necessary to reduce the pack to the thickness and cross-sectional contour which has been predetermined.

- ALEXANDER PATERSON. 

